Softwood Pinus radiata was degraded by the ascomycete Chrysonilia sitophila during 3 months. The total weight loss of the wood was 20% and the carbohydrate and lignin losses were 18% and 25%, respectively. Decayed wood was extracted with solvents of increasing polarity. Methanol and dioxane yielded extracts containing representative low molecular weight degraded lignins. The overall structure of the degraded lignins, as shown by U.V./visible, I.R., H-1 and C-13 NMR spectroscopy, GPC, functional group and elemental analyses, was compared with the structure of milled wood lignin extracted from undecayed P. radiata. The compilation of the data allows us to suggest oxidative C alpha-C beta and beta-O-aryl cleavages for the mechanism of lignin degradation by this ascomycete. New saturated carbons on the side chain of the degraded lignins were detected. Based on these data a reductive ability of this microorganism was also suggested.64265274